题目内容
物体在如图所示的合外力的作用下从静止开始做直线运动。设该物体在
和
时刻相对于出发点的位移分别是
和
,速度分别是
和
,合外力从开始至
时刻做的功是
,从
至
时刻做的功是
,则 ( )
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241708599271254.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170856510319.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170856838408.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170857150300.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170857384331.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170857852298.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170858211330.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170856510319.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170858663423.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170856510319.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170856838408.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170859615448.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241708599271254.png)
A.![]() | B.![]() ![]() |
C.![]() | D.![]() |
BC
试题分析:由于物体受的合力是2倍的关系,根据牛顿第二定律
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170902064503.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170902438482.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170902828702.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170903078518.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170903561668.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/201408241709041541745.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170904794716.png)
![](http://thumb.1010pic.com/pic2/upload/papers/20140824/20140824170905199971.png)
所以BC正确.
故选BC.
点评:本题在计算时要注意,位移x1和x2都是相对于出发点的位移,并不是各自时间内经过的位移.
![](http://thumb2018.1010pic.com/images/loading.gif)
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